Earlier techniques relating to OFDM (Orthogonal Frequency Division Multiplex) modulation/demodulation and earlier techniques relating to modulation/demodulation using a unitary matrix are disclosed in the literatures indicated below.
[Patent Literature 1] Unexamined Japanese Patent Application KOKAI Publication No. 2002-261727
[Patent Literature 2] Unexamined Japanese Patent Application KOKAI Publication No. 2001-320344
[Patent Literature 3] Unexamined Japanese Patent Application KOKAI Publication No. 2001-36445
[Non-Patent Literature 1] Chang-Jun AHN and Iwao SASASE, Convolutional Coded Coheretn and Differential Unitary Space-Time Modulated OFDM with Bit Interleaving for Multiple Antenna System, technical report of IEICE, TECHNICAL REPORT OF IEICE, SST2002-47, October 2002, pp. 75-80
Patent Literature 1 discloses an invention relating to a multi-carrier signal transmitter apparatus used in digital wireless communications.
Particularly, the literature discloses an OFDM signal transmitter apparatus which is designed to supply a same single local oscillation signal output from a single local oscillator to a plurality of transmitter side frequency converters corresponding to a plurality of antennas respectively, and which can realize high-speed transmission by improving frequency utilization efficiency while maintaining the orthogonality of the carriers in the plurality of antennas.
Patent Literature 2 discloses an invention relating to channel estimation by clustered OFDM receiver apparatuses.
Particularly, the literature discloses an invention which supplies signals having come to one or more antennas through respective transmission channels to corresponding FFT elements, filters the outputs from the FFT elements, combines the filtered signals, and supplies the combined signal to a threshold element, and which uses a unique matrix of a frequency-domain correlation matrix of each channel as the optimum channel estimator, wherein the matrix is dependent on the delay profile of each channel.
Patent Literature 3 discloses an invention relating to a diversity receiving device for mobile transmitter apparatus, which performs bandwidth-division diversity reception by using a plurality of received signals having the same frequency, and employs simultaneous FFT, thereby to reduce the size of the apparatus and improve its mobility.
Particularly, the literature discloses a diversity receiving device which requires no more than one cable, and has an FFT means for obtaining frequency axis data by fast Fourier transform, and a selecting/combining output means for calculating differences between symbols of the frequency axis data and selecting or combining differentially demodulated carrier data of OFDM signals obtained by the difference calculation to output the selected or combined data.
Non-Patent Literature 1 is a paper of a past study joined by one of the inventors listed in the present application, and discloses an invention which performs space-time modulation/demodulation by a unitary matrix, and transmits signals at different times with the use of a plurality of antennas.
Notwithstanding these techniques, various other communication techniques applicable to OFDM communications are strongly demanded.
The present invention was made to solve the above-described problem, and an object of the present invention is to provide a transmitter apparatus, a receiver apparatus, a transmitting method, and a receiving method for performing efficient communication by using modulation/demodulation by a unitary matrix in which components other than the diagonal components are 0, and a program for realizing these on a computer.